1. Field of the Invention
The present invention relates to antenna systems and more particularly to an antenna system and method for implementing and maintaining a matched condition for an antenna system.
2. Related Art
The vast majority of antennas used in communication systems to date have been passive antennas that are impedance matched over a set frequency range. The antenna is typically connected to a transceiver which contains a transmitter and/or a receiver. The antenna and transceiver combination are used to transmit and receive signals over the set frequency range. If changes to the environment in the vicinity of the antenna occur, the antenna can de-tune. The de-tuning of the antenna is caused by a change in impedance properties of the antenna related to environmental changes such as portions of a human body being positioned close to the antenna, or wood, metal, or plastic objects becoming positioned in close proximity to the antenna. The change in antenna impedance properties results in an increase in reflected power at the antenna/transceiver junction; this increase in reflected power results in less power transmitted by the antenna in the transmit mode, and less power received by the antenna when in the receive mode.
As communication systems become more complex, the frequency range required for the antenna to operate increases, thereby placing an increased burden on the antenna designer to impedance match the antenna over a larger frequency range. The use of communication systems in dynamic environments, where changes to the local environment in the vicinity of the antenna can cause de-tuning of the antenna impedance, can result in degraded communication system performance.
Recent trends in radiofrequency (RF) component technology have resulted in improved performance from tunable components such as RF switches, tunable capacitors, and MEMS devices. The improved performance achieved by these new components can be measured in component efficiency characteristics, size, and cost.